Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Evaluating the Potential Benefits and Sustainability of a Novel Living and Dead Cover Crop Mixture in Mid-Atlantic Crop Production(2023) Johnson, Veronica; Hooks, Cerruti RR; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Modern vegetable production systems are often characterized by monoculture fields andthe intensive use of tillage and/or synthetic agrochemicals for managing weeds and insect pests. A growing public interest in more sustainable and eco-friendly production practices has resulted in increased demand that crops be produced with lower inputs. Incorporating flowering living mulches and cover crop residues within crop fields can create an environment more hospitable to beneficial organisms and less conducive to pest outbreaks. My dissertation research aims to advance our knowledge in this area by evaluating the impacts of a novel cover cropping tactic which involves combining a perennial flowering living mulch with cover crop residue on insects and/or weeds. Further, it is often suggested that weed management requires a holistic approach; and that cover cropping will not be successful as a sole weed management tactic. As such, another research aim is to investigate whether combining a cover cropping tactic with herbicide sprays would result in better weed suppression and increased yield in sweet corn compared to using cover crops alone. An economic assessment was also performed to further evaluate the practicality of sweet corn producers adopting the management practices being investigated. Cost of seeds, labor and other expenses can be a primary limitation to cover crop usage. To this point, I also evaluated the feasibility of using a single cover crop planting to suppress weeds over multiple cropping systems and field seasons. If a single cover crop planting can be used over multiple seasons, this could reduce the cost of cover crop use. Agricultural intensification and conversion of natural landscapes to crop production fields have contributed to declines in insect biodiversity including natural enemies and pollinators. Advancing our understanding of how increasing vegetational diversity within crop fields influences weed pressure and populations of herbivores and beneficial arthropods, as well as production costs, can facilitate the adoption of practices in annual cropping systems that favor beneficial organisms and conserves insect biodiversity.Item Effects of post-harvest management practices on the degradation of Bacillus thuringiensis proteins in genetically modified corn residue(2018) Johnson, Veronica; Hooks, Cerruti RR; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Most studies addressing the ecological effects of Bt crops have focused on non-target effects during the crop growing cycle. Less information is available on the fate of expressed toxins in crop residue after harvest in a no-till production system. This research investigated the effects of four post-harvest management practices on the degradation rates of Cry proteins expressed in SmartStax field corn. Cry protein degradation expressed as growth inhibition of Ostrinia nubilalis larvae after harvest was measured by a feeding bioassay, and enzyme-linked immunosorbent assays were used to detect the presence of Cry proteins. Cry proteins retained significant levels of biological activity at crop senescence and were still present in corn residue for more than 20 weeks after harvest. Despite inconsistencies in treatment effects, the study demonstrated that post-harvest practices that increase soil-residue contact increase protein degradation, thereby reducing the period of exposure for non-target organisms.